Method for producing metal thin film

ABSTRACT

A method for producing a metal thin film on a substrate includes: a step of applying an ink to a flat blanket; a first transfer step of bringing the first blanket and a letterpress having a predetermined pattern of projections into contact by a pressure compression while the flat blanked and the letterpress being disposed opposite each other, to selectively transfer a portion of the ink on the flat blanket corresponding to the projections to the letterpress; a second transfer step of bringing the flat blanket obtained after the first transfer step and the substrate into contact by pressure compression while the flat blanket and the substrate being disposed opposite each other, to transfer the ink remaining on the flat blanket to the substrate; and a step of subjecting the substrate obtained after the second transfer step to electroless plating to deposit a metal thin film on the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/233,581, titled “METHOD FOR PRODUCING METAL THIN FILM,” filed on Sep.15, 2011, which is a continuation of U.S. patent application Ser. No.12/157,473, titled “METHOD FOR PRODUCING METAL THIN FILM,” filed on Jun.11, 2008, which claims the benefit under 35 U.S.C. §119 of JapanesePatent Application JP 2007-158341, filed in the Japanese Patent Officeon Jun. 15, 2007. The contents of these applications are herebyincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing a metal thinfilm using a reverse offset printing method.

2. Description of Related Art

Some methods for producing a thin film pattern utilizing a reverseoffset printing method have been proposed (for example, PatentUnexamined Patent Application Publication No. 11-58921 (hereinafterreferred to as “Patent Document 1” and Patent Unexamined PatentApplication Publication No. 2006-278845 (hereinafter referred to as“Patent Document 2”)).

In the Patent Document 1, a method is proposed in which a desired resinthin film pattern is formed on a substrate by a reverse offset printingmethod using a cylindrical blanket comprising a cylindrical roll havinga silicone resin formed thereon and using a letterpress having formed adesired pattern.

In the Patent Document 2, a method is proposed in which a desiredconductive thin film pattern is formed on a substrate by a reverseoffset printing method using an ink including conductive fine particles(having an average particle size of 50 nm or less) mixed into awater-soluble resin (polyethylene oxide).

SUMMARY OF THE INVENTION

In the Patent Document 1, a cylindrical blanket is used in the reverseoffset printing. Consequently, it is difficult to keep uniform thecontact pressure of the cylindrical blanket to the whole of a substratewhich is flat during the transfer to the substrate, and a portion of thepattern becomes illegible. In addition, in bringing the cylindricalblanket and the flat substrate into contact, the alignment of them isnot easy. Thus, the yield in producing a thin film is lowered.

Further, in the Patent Document 1, a resin thin film to be used mainlyas an etching resist is formed on a substrate, and, for producing, e.g.,a conductive thin film (metal thin film) on a substrate, a metal thinfilm is deposited on the entire surface of the substrate and then aresin ink is printed thereon, and further a step of removing the resinink by etching so that the resin ink has a predetermined pattern isrequired, thus increasing the number of steps.

On the other hand, in the Patent Document 2, conductive fine particlesare mixed into the ink, and a conductive thin film is directly formed ona substrate using the conductive fine particles. Further, in the PatentDocument 2, the shape of the blanket is not limited to the cylindrical,and it is considered that a flat blanket may be applied to the method.

However, in the Patent Document 2, as described above, a resin(water-soluble resin) is also contained in the ink, and the resultantconductive thin film has a resistance larger than the resistance of athin film composed solely of conductive fine particles. Further, the inkis a mixture of the conductive fine particles and resin, and hence theink applied to the blanket has an increased thickness, making itdifficult to achieve a scaled-down pattern.

Accordingly, it is desirable to provide a method for producing a metalthin film, which achieves a finer pattern and a higher yield than thoseobtained by a known method without unnecessarily increasing theresistance of the thin film.

In accordance with an embodiment of the present invention, there isprovided a method for producing a metal thin film including thefollowing requirements (A) to (E):

(A) an application step of applying an ink to a flat blanket;

(B) a first transfer step of bringing the flat blanket and a letterpresshaving a predetermined pattern of projections into contact by a pressurecompression while the flat blanket and the letter press being disposedopposite each other, to selectively transfer a portion of the ink on theflat blanket corresponding to the projections to the letterpress;

(C) a second transfer step of bringing the flat blanket obtained afterthe first transfer step and the substrate into contact by a pressurecompression while the flat blanket and the substrate being disposedopposite each other, to transfer the ink remaining on the flat blanketto the substrate;

(D) a plating step of subjecting the substrate obtained after the secondtransfer step to electroless plating to deposit a metal thin film on thesubstrate; and

(E) the ink including a catalyst material for the electroless plating isused.

In the method for producing a metal thin film of an embodiment of thepresent invention, the substrate to which the ink including a catalystmaterial is transferred is subjected to electroless plating. As aresult, in the plating step, a metal thin film is selectively formed onthe substrate in a region to which the ink is transferred. The ink istransferred to the substrate using a flat blanket, and further thesubstrate and the flat blanket are in contact by pressure compression inthe transfer step. Accordingly, the letterpress or substrate and theblanket are easy to align and the whole pressure for the contact of themis uniform. Further, the ink does not contain a material for the metalthin film but a catalyst material for the electroless plating. As aresult, the resultant metal thin film has a low resistance, as comparedto a conventional metal thin film formed using an ink containing amaterial for the metal thin film and a resin, and further the inkapplied to the flat blanket has a reduced thickness, thus making it easyto achieve a scaled-down pattern.

The above summary of the present invention is not intended to describeeach illustrated embodiment or every implementation of the presentinvention. The figures and the detailed description which follow moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are cross-sectional views showing part of the principalsteps in a method for producing a metal thin film according to oneembodiment of the present invention.

FIGS. 2A to 2C are cross-sectional views showing steps subsequent toFIG. 1C.

FIG. 3 is a cross-sectional view showing a step subsequent to FIG. 2C.

FIGS. 4A and 4B are cross-sectional views showing an example of a methodfor bringing the flat blanket and the letterpress into contact.

FIG. 5 is a cross-sectional view showing another example of a method forbringing the flat blanket and the letterpress into contact.

FIG. 6 is a cross-sectional view showing an example of a method forseparating the flat blanket and the letterpress.

FIG. 7 is a cross-sectional view showing another example of a method forseparating the flat blanket and the letterpress.

FIGS. 8A and 8B are cross-sectional views showing an example of a methodfor bringing the flat blanket and the substrate into contact.

FIG. 9 is a cross-sectional view showing another example of a method forbringing the flat blanket and the substrate into contact.

FIGS. 10A and 10B are a cross-sectional view and a plan view showing anexample of a method for alignment in bringing the flat blanket and thesubstrate into contact.

FIGS. 11A and 11B are cross-sectional views showing examples of flatblankets having formed alignment marks.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinbelow, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIGS. 1 to 3 are cross-sectional views for explaining a method forproducing a metal thin film according to one embodiment of the presentinvention.

First, as shown in FIG. 1A, an ink 2 is applied to a flat blanket 1. Theflat blanket 1 includes a rigid base 11 composed of a glass plate, ametal plate, or the like, and a polydimethylsiloxane (PDMS) layer 12 onthe base 11. An ink is applied to the PDMS layer 12. By forming theflexible PDMS layer on the rigid base 11, the accuracy in the planedirection is improved and the transfer pressure is reduced. It ispreferable that the base 11 has a thickness of about 10 to 500 μm andthe PDMS layer 12 has a thickness of 1 to 5,000 μm.

With respect to the ink 2, an ink including a catalyst material whichserves as a catalyst for the below-mentioned electroless plating andbeing suitable for the printing method (reverse offset printing method)is used. Specifically, it is preferable that the ink 2 contains, as asolute, a metal compound or metal fine particles (metal nanoparticles)which is the catalyst material, and that the ink 2 contains, as asolvent, a nonpolar solvent having a boiling point of 100° C. or lowerand having a contact angle of 10° or less on the PDMS layer 12, which isdescribed in detail below. The solute and the solvent are mixed togetherto form the ink 2. It is preferable that the ink 2 has a concentrationof 0.01 to 30% by weight, but the concentration of the ink is notlimited to this range.

With respect to the metal compound, there may be used a compound of ametal, such as gold (Au), silver (Ag), or palladium (Pd), having bondedthereto at least one organic compound selected from a linear fatty acidrepresented by the molecular formula: C_(n)H_(m)COOH, a linearalkylamine represented by the molecular formula: CH₃(CH₂)_(n)NH₂, alinear alkylthiol represented by the molecular formula: CH₃(CH₂)_(n)SH,and a linear alkylnitrile represented by the molecular formula:CH₃(CH₂)_(n)CN. In these molecular formulae, it is preferable that n isan integer of 5 to 40 and m satisfies: m=2n+1.

With respect to the metal nanoparticles, fine particles (desirablyhaving an average particle size of 0.1 to 20 nm) of a metal, such as Au,Ag, or Pd, may be used, and fine particles having their surfaces coveredwith a protective agent composed of an organic compound are desirablyused. The protective agent enables the metal nanoparticles to be stablystored. With respect to the protective agent, there may be used onehaving bonded at least one organic compound selected from a linearalkylamine represented by the molecular formula: CH₃(CH₂)NH₂, a linearalkylthiol represented by the molecular formula: CH₃(CH₂)_(n)SH, and alinear alkylnitrile represented by the molecular formula:CH₃(CH₂)_(n)CN. In these molecular formulae, it is preferable that n isan integer of 5 to 40 and m satisfies: m=2n+1.

With respect to the solvent of the ink 2, as described above, a nonpolarsolvent having a boiling point of 100° C. or lower and having a contactangle of 10° or less on the PDMS layer 12 is preferable. When thesolvent having a boiling point of 100° C. or lower is used, almost allthe solvent is evaporated during the application of the ink 2 or aftercompletion of the application, so that only the solute, which serves asa catalyst for the electroless plating, remains on the flat blanket 1.Examples of the solvents include hydrocarbons, e.g., linear alkanes,such as pentane, hexane, and heptane, cycloalkanes, such as cyclopentaneand cyclohexane, and ethers, such as ethyl methyl ether, diethyl ether,and tetrahydrofuran.

With respect to the method for applying the ink 2 to the flat blanket 1,for example, a spin coating method, a spraying method, a CAP coatingmethod, a slit coating method, an LB film producing method, or an inkjetmethod is preferred.

Subsequently, as shown in FIG. 1B, the flat blanket 1 and a letterpress3 having a predetermined pattern of projections are disposed opposite toeach other, and are brought into contact to selectively transfer aportion of the ink 2 on the flat blanket 1 corresponding to theprojection 31 to the letterpress 3.

The letterpress 3, which is composed of quartz, glass, a resin, a metal,or the like and which has depressions 32 each having a depth of about0.1 to 10 μm formed using, e.g., a photolithography method and anetching method, is desirably used. As described below, a pattern to beformed to letterpress 3 is configured in such a manner that thedepressions 32 corresponds to a region in which a metal thin film (metalwiring) is formed.

To bring the flat blanket 1 and the letterpress 3 into contact, they arecontacted by pressure compression (using a compressed gas pressuremethod). The compressed gas pressure method is a method in which theflat blanket 1 and letterpress 3 to be in contact are disposed oppositeand close to each other and fixed to predetermined stages, andcompressed gas is injected from the back side of one of the flat blanket1 and the letterpress 3 to push it, bringing the flat blanket 1 andletterpress 3 into contact. In this instance, a space defined by theobject to be push and the stage as a source of the compressed gas isclosed (space indicated by an arrow P1 in FIGS. 4A and 4B or spaceindicated by an arrow P4 in FIG. 5).

Specifically, for example, as shown in FIG. 4A, the outer edge of theflat blanket 1 is mechanically fixed by a lower stage 51, O-rings 53A,53B, and stationary frames 54A, 54B, and further the letterpress 3 isfixed by an upper stage 52, and compressed gas is injected through anopening 510 (which functions as a vacuum port and a compressed gasinlet) formed around the center of the lower stage 51 to push the flatblanket 1. Alternatively, for example, as shown in FIG. 4B, the outeredge of the flat blanket 1 may be fixed by vacuum suction, as indicatedby reference characters P2, P3, through openings 511A, 511B formed in alower stage 51A. Further alternatively, for example, as shown in FIG. 5,the letterpress 3 is fixed to a lower stage 51 and the outer edge of theflat blanket 1 is fixed by stationary frames 54C, 54D, and further anexpandable and stretchable film 55 having flexibility is fixed byO-rings 53A, 53B, stationary frames 54A, 54B, and an upper stage 52A,and compressed gas is injected through an opening 520 (which functionsas a vacuum port and a compressed gas inlet) formed around the center ofthe upper stage 52A to push the stretchable film 55 and flat blanket 1.In this case, the outer edge of the flat blanket 1 is just mechanicallyfixed. In the above cases, the distance between the flat blanket 1 andthe letterpress 3 is 1 μm to 1 mm, and the transfer pressure isprecisely controlled to be about 0.1 to 100 kPa. Thus the pressure onthe flat blanket 1 can be controlled to be uniform and low, enablingtransfer of the ink 2 free of batter. In FIGS. 4 to 11 including FIGS. 4and 5, the inks 2, 2A, 2B are not shown.

Subsequently, as shown in FIG. 1C, the flat blanket 1 and letterpress 3brought into contact each other are separated. As a result, the inkremains on the flat blanket 1 in a region to which the ink is nottransferred by the letterpress 3 (portion of the ink 2A shown in thefigure) to form a pattern of the metal thin film (metal wiring)described later. On the other hand, the ink is transferred to theprojection 31 of the letterpress 3 (portion of the ink 2B shown in thefigure). Examples of methods for separating the flat blanket 1 and theletterpress 3 include a method in which, for example, as shown in FIG.6, the flat blanket and the letterpress are separated by creating avacuum in the space P1 by evacuation through the opening 510 (see anarrow P5 shown in the figure) to allow the flat blanket 1 to adsorb ontothe lower stage 51, and a method in which, for example, as shown in FIG.7, the flat blanket and the letterpress are mechanically separated bymoving upward the outer edge of the flat blanket 1 (see arrows P61, P62shown in the figure).

Subsequently, as shown in FIG. 2A, the flat blanket 1 to which the ink2A has been transferred and a substrate (substrate 40) on which a metalthin film will be formed are disposed opposite to each other and broughtinto contact to transfer the ink 2A remaining on the flat blanket 1 tothe substrate 40.

With respect to the substrate 40, a substrate composed of a materialsuch as silicone, synthetic quartz, glass, a metal, a resin, or a resinfilm, is used. It is preferable that the substrate 40 includes anadhesion layer 41 formed thereon so that the ink 2A is transferred tothe adhesion layer 41 because the ink 2A is easy to bond. Examples ofmaterials for the adhesion layer 41, include materials including atleast one compound selected from an amino silane compound, a mercaptosilane compound, a phenyl silane compound, and an alkyl silane compound.The adhesion layer 41 may be formed on the substrate 40 using a spincoating method, a dipping method, a thermal chemical vapor deposition(CVD) method, or the like.

To bring the flat blanket 1 and the substrate 40 into contact, they arecontacted by pressure compression (using a compressed gas pressuremethod) as described above. Specifically, for example, as shown in FIG.8A, the outer edge of the flat blanket 1 is mechanically fixed by alower stage 51, O-rings 53A, 53B, and stationary frames 54A, 54B, andfurther the substrate 40 is fixed by an upper stage 52, and compressedgas is injected through an opening 510 (which functions as a vacuum portand a compressed gas inlet) formed around the center of the lower stage51 to push the flat blanket 1. Alternatively, for example, as shown inFIG. 8B, the outer edge of the flat blanket 1 may be fixed by vacuumsuction, as indicated by reference characters P2, P3, through openings511A, 511B formed in a lower stage 51A. Further alternatively, forexample, as shown in FIG. 9, the substrate 40 is fixed to a lower stage51 and the outer edge of the flat blanket 1 is fixed by stationaryframes 54C, 54D, and further a stretchable film 55 is fixed by O-rings53A, 53B, stationary frames 54A, 54B, and an upper stage 52A, andcompressed gas is injected through an opening 520 (which functions as avacuum port and a compressed gas inlet) formed around the center of theupper stage 52A to push the stretchable film 55 and flat blanket 1. Inthis case, the outer edge of the flat blanket 1 is just mechanicallyfixed. In the above cases, the distance between the flat blanket 1 andthe substrate 40 is 1 μm to 1 mm, and the transfer pressure is preciselycontrolled to be about 0.1 to 100 kPa. Thus the pressure on the flatblanket 1 can be controlled to be uniform and low, enabling transfer ofthe ink 2A free of batter.

It is preferable that a predetermined alignment mark is formed on thesubstrate 40 and the substrate 40 and the flat blanket 1 are aligned(alignment) using the alignment mark in bringing the flat blanket 1 andsubstrate 40 into contact to transfer the ink 2A. This is because thealignment can be easily improved in accuracy.

Specifically, for example, as shown in FIG. 10A, an alignment mark (notshown) formed by the ink 2A on the flat blanket 1 and an alignment mark(not shown) preliminarily formed on the substrate 40 are compared usingan alignment microscope 6 (61, 62) to adjust the X, Y, θ coordinates(see FIG. 10B), making an alignment. Therefore, for example, as shown inFIG. 10B, the transfer apparatus has a control mechanism for the X, Y, θcoordinates in one of the upper and lower stages 51, 52. If the distancebetween the flat blanket 1 and the substrate 40 is large (for example,30 μm or larger), the alignment microscope 6 lacks the focal depth,making it difficult to put together the alignment marks. Accordingly, insuch a case, it is preferable that the apparatus has a multifocalalignment mechanism having an image recording function.

If the thickness of the ink 2A is too small to observe the alignmentmark of the ink 2A using the alignment microscope 6, it is preferablethat, for example, shown in a flat blanket 1A or 1B of FIG. 11A or 11B,alignment marks 13A, 13B are preliminarily formed on the PDMS film 12 oralignment marks 13C, 13D are formed in advance on the base 11. Since thePDMS film 12 is transparent, the alignment marks 13C, 13D can berecognized in the case of FIG. 11B. In these cases, a first alignment inwhich the flat blanket 1 and the letterpress 3 are aligned is performedand the ink is transferred to determine the relationship in positionbetween the alignment mark on the flat blanket 1 and the ink pattern,and then a second alignment in which the flat blanket 1 and thesubstrate 40 are aligned is performed and the ink is transferred.

Subsequently, as shown in FIG. 2B, the flat blanket 1 and substrate 40bought into contact each other are separated. As a result, the whole ofink 2A on the flat blanket 1 is transferred to the substrate 40(adhesion layer 41) to form a pattern of the metal thin film (metalwiring) described later, and, on the other hand, no ink remains on theflat blanket 1. As examples of methods for separating the flat blanket 1and the substrate 40, include the method as described above in which theflat blanket and the substrate are separated by creating a vacuum in thespace P1 by evacuation through the opening 510 to allow the flat blanket1 to adsorb onto the lower stage 51 and method in which the flat blanketand the substrate are mechanically separated by moving upward the outeredge of the flat blanket 1.

Subsequently, as shown in FIG. 2C, organic substances contained in thesolvent of the ink 2A or the protective film for the metal nanoparticlesare removed to activate the catalyst material for electroless plating(specifically, the solute of the ink 2A), thus promoting the electrolessplating described later. The ink 2A containing a great amount of organicsubstances is likely to be inactive in the electroless plating, andtherefore the organic substances are removed so that the ink fullyexhibits catalytic activity. A treatment for the activation is made by,for example, an ultraviolet (UV) ozone treatment in which the ink 2A isirradiated with ultraviolet light L0 as shown in the figure, ozone watercleaning, or baking treatment. The UV ozone treatment or ozone watercleaning may be performed at a relatively low temperature (e.g., atabout 0 to 200° C.). The baking treatment is performed at a relativelyhigh temperature, e.g., at about 200 to 400° C. With respect to thebaking treatment, when the ink 2A contains Pd as a solute (catalystmaterial), for preventing Pd from suffering oxidization, it ispreferable that the baking treatment is performed in an oxygen freeatmosphere, such as nitrogen gas (N₂) or argon (Ar).

Subsequently, the substrate 40 to which the ink 2A has been transferredis subjected to electroless plating to deposit a metal thin film 42 onthe substrate 40 as shown in FIG. 3. Specifically, the metal thin film42 is selectively formed on the substrate 40 in a region to which theink 2A is transferred. In the electroless plating, the substrate 40 isimmersed in a desired electroless plating solution to selectivelydeposit a metal on the substrate only in a region in which the ink 2A ispresent. In the electroless plating, various metals, such as nickel(Ni), copper (Cu), cobalt (Co), iron (Fe), Au, or Ag, can be deposited.

Finally, the metal thin film 42 deposited on the substrate 40 isannealed at about 100 to 1,000° C. In this case, the metal thin film 42may be reduced in resistance, the stress may be relaxed duringdeposition of the metal thin film, the adhesion of the metal thin filmmay be improved, or metal oxidization may be prevented. For preventingthe metal thin film 42 from suffering oxidization during the annealing,it is preferable that the annealing is performed in a vacuum or in anoxygen free atmosphere, such as N₂ or Ar.

Thus, the metal thin film (metal thin film 42) according to anembodiment of the present invention is produced.

In the method for producing a metal thin film (metal thin film 42)according to an embodiment of the present invention, the substrate 40 towhich the ink 2A comprising a catalyst material has been transferred issubjected to electroless plating. As a result, the metal thin film 42 isselectively formed on the substrate 40 in a region to which the ink 2Ais transferred.

The ink 2A is transferred to the substrate 40 using the flat blanket 1,and further the substrate and the flat blanket are in contact bypressure compression in the transfer step (steps shown in FIG. 1B andFIG. 2A) (using a compressed gas pressure method). As a result, theletterpress 3 or substrate 40 and the flat blanket 1 is easy to alignand the whole pressure for the contact of them is uniform.

The ink 2 does not contain a material for the metal thin film 42 but acatalyst material for the electroless plating. Accordingly, theresultant metal thin film 42 has a low resistance, as compared to aknown metal thin film formed using an ink containing a material for themetal thin film and a resin, and further the ink 2 applied to the flatblanket 1 has a reduced thickness, thus making it easy to achieve ascaled-down pattern.

As described above, according to an embodiment of the present invention,the substrate 40 to which the ink 2A comprising a catalyst material hasbeen transferred is subjected to electroless plating. As a result, andthe metal thin film 42 is selectively formed on the substrate 40 in aregion to which the ink 2A is transferred. The ink 2 is transferredusing the flat blanket 1, and further the substrate and the flat blanketare in contact by pressure compression in the transfer step.Consequently, the letterpress or substrate and the blanket is easy toalign and the whole pressure for the contact of them is uniform, thusimproving the yield in producing the metal thin film 42. Further, theink 2 does not contain a material for the metal thin film 42 but acatalyst material for the electroless plating. Accordingly, the metalthin film 42 has a low resistance and the pattern can be easily scaleddown, as compared to those obtained in a known method. Thus, a finerpattern and a higher yield than those obtained by a known method can beachieved without unnecessarily increasing the resistance of the thinfilm.

Since an activating step, in which the catalyst material is activated,includes between the transfer step of the ink 2A (step shown in FIG. 2A)and the plating step (step shown in FIG. 3), the electroless plating ispromoted, so that the formation of the metal thin film 42 can bepromoted.

When the substrate 40 and the flat blanket 1 individually have formedthereon alignment marks in advance and the substrate 40 and the flatblanket 1 are aligned using the alignment marks in the transfer step ofthe ink 2A, the alignment is easily improved in accuracy, and furtherthe yield can be improved.

EXAMPLES

Hereinbelow, embodiments of the present invention will be described inmore detail with reference to the following Examples.

Example 1

A metal thin film having a structure shown in FIG. 3 was formed asfollows. Specifically, an ink 2 including a palladium (Pd) particlecolloid, which is a metal compound corresponding to a catalyst materialfor the electroless plating, was prepared, and the ink 2 was printed ona substrate 40 by a reverse offset printing method, and then a Cu thinfilm was selectively deposited on the ink by Cu electroless plating toform a Cu wiring.

The ink 2 contained a Pd particle colloid {hydrophobic Pd decylamine(DA) colloid toluene solution, manufactured and sold by Tanaka KikinzokuKogyo} which is a metal compound corresponding to a catalyst materialfor the electroless plating, and the Pd particle colloid treated by thefollowing procedure was used. The hydrophobic Pd DA colloid toluenesolution was first adjusted in concentration to 1.0% by weight, andn-hexadecanethiol was added to the solution so that the concentrationbecame 2.0% by weight, and the resultant mixture was heated at 80° C.for 12 hours while stirring. Then, the mixture was cooled to roomtemperature, and methanol was added to the mixture in an amount about 20times the amount of the Pd DA colloid toluene solution to effectprecipitation of Pd particles. Then, the resultant precipitates andsolution were subjected to filtration using a 1 μm filter to recover theprecipitates on the filter. In the precipitates, decylamine in part ofthe protective agent for the Pd particles is substituted byhexadecanethiol in the above treatment. The substitution ratio is 10 to30% when decylamine is 100. By the above treatment, the Pd particles canbe dissolved in hexane or pentane, in which the untreated Pd particleshave a low solubility. The Pd particles were dispersed in an n-pentanesolution so that the concentration became 1.0% by weight, and then usedin the ink.

The flat blanket 1 having a polydimethylsiloxane (PDMS) layer 12deposited (by a spin coating method) on glass (thickness: 0.2 mm; AF45,manufactured and sold by SCHOTT AG) as a base 11 was baked at 65° C. for12 hours and then used. The PDMS layer 12 had a thickness of 60 μm. Asthe PDMS, SYLGARD184 (manufactured and sold by Dow Corning Toray Co.,Ltd.) was diluted with toluene in a concentration of 80% by weight andthen used.

First, in the application step of the ink 2 (FIG. 1A), the ink 2 wasapplied to the flat blanket 1 by a spin coating method. Conditions forapplication at 3,000 rpm held for 20 seconds were employed, and thelayer of the ink 2 had a thickness of 20 nm.

Next, in the first transfer step (FIG. 1B), the flat blanket 1 and aletterpress 3 were brought into contact using a compressed gas pressuremethod to selectively transfer to the letterpress 3 an ink 2B in the ink2 corresponding to the projection 31. The letterpress 3 was composed ofquartz glass. Specifically, a chromium (Cr) film having a thickness ofabout 200 nm was deposited on quartz glass by a vacuum evaporationmethod, and a predetermined pattern was formed in the resultant film bya photolithography method and a wet etching method, and the quartz glasswas etched in about 1.0 μm by a dry etching method, and finally the Crwas removed by etching, thus preparing a letterpress 3 havingprojections 31 and depressions 32. In bringing the flat blanket 1 andthe letterpress 3 into contact, as shown in FIG. 5, the flat blanket 1was fixed by a lower stage 51 and stationary frames 54C, 54D, and theflat blanket 1 and the letterpress 3 were disposed opposite and parallelto each other with a distance of 1 mm between them, and then compressedair was injected from the back side of the flat blanket 1 (opening 520)to push the expanded film (stretchable film 55) made of a fluororesin,bringing the flat blanket and the letterpress into contact. The transferpressure was 10 kPa, and the transfer time was 10 seconds.

Then, as shown in FIG. 1C and FIG. 7, the flat blanket 1 and theletterpress 3 were separated from each other by moving upward thestationary frames 54C, 54D.

Next, in the second transfer step (FIG. 2A), the flat blanket 1 and thesubstrate 40 were brought into contact using a compressed gas pressuremethod to transfer the ink 2A on the flat blanket 1 to the substrate 40.As a result, a pattern of the ink containing the Pd particle colloid wasformed on the substrate 40. An adhesion layer 41 for bonding the ink 2Awas formed on the substrate 40 in advance. As a material for theadhesion layer 41, 3-mercaptopropyltrimethoxysilane {HSC₃H₆Si(OCH₃)₃},which is a mercapto silane compound, diluted with ethyl lactate in aconcentration of 50 mmol/L was used. This compound was deposited on thesubstrate 40 composed of glass by a spin coating method and annealed at120° C. for 30 minutes, and rinsed with ethanol by ultrasonic cleaningfor 10 minutes and then used. The detailed conditions for the secondtransfer step are basically the same as the conditions for the firsttransfer step (FIG. 1B). Since there was no pattern preformed on thesubstrate 40 in the present Example, the flat blanket 1 and thesubstrate 40 were aligned by roughly putting together their centers withvisual estimation.

Then, as shown in FIG. 2B, the flat blanket 1 and the substrate 40 wereseparated from each other by moving upward the stationary frames 54C,54D.

Next, the substrate 40 was baked in an atmosphere of nitrogen gas at200° C. for 5 minutes to decompose organic substances contained in theink 2A, whereby the ink fully exhibited catalytic activity in theelectroless plating.

Finally, the substrate 40 thus prepared was subjected to Cu electrolessplating. As an electroless plating solution, OPC COPPER T, manufacturedand sold by Okuno Chemical Industries Co., Ltd., was used. Thus, a Cuwiring composed of a Cu thin film having a thickness of 500 nm wasformed. The wiring had a fineness of 5 μm/5 μm in terms of a line/space.

Example 2

A metal thin film was formed in substantially the same manner as inExample 1 except for the items shown below. Specifically, an ink 2including Pd nanoparticles (protective agent: C₁₆H₃₃SH), which are metalnanoparticles corresponding to a catalyst material for the electrolessplating, was prepared, and the ink 2 was printed on a substrate 40 by areverse offset printing method, and then an Ni thin film was selectivelydeposited on the ink by Ni electroless plating to form an Ni wiring.

The ink 2 contained Pd nanoparticles (protective agent: C₁₆H₃₃SH) havingan average particle size of 8 nm, which are metal nanoparticlescorresponding to a catalyst material for the electroless plating,dispersed in tetrahydrofuran in a concentration of 1.0% by weight.

In this Example, an alignment mark was formed on the substrate 40 inadvance, and the alignment accuracy in the printing was evaluated. Inthe printing step, as shown in FIG. 10, in the stage for fixing andpushing the flat blanket 1, an apparatus having a control mechanism forthe X, Y, θ coordinates and a parallel control mechanism was used. Aspacer kept the flat blanket 1 and the substrate 40 parallel, and theflat blanket 1 and the substrate 40 were aligned while keeping themparallel and maintaining a gap of 50 μm. A specific alignment wasperformed in such a manner that the alignment mark preformed on thesubstrate 40 and the alignment mark formed on the flat blanket 1 in thefirst transfer step (FIG. 1B) were put together. The alignment accuracymeasured after the second transfer step (FIG. 2A) was within ±0.5 μm.

In this Example, as shown in FIG. 2C, the substrate 40 was subjected toUV ozone treatment to decompose organic substances contained in the ink2A, so that the ink fully exhibited catalytic activity in theelectroless plating.

In this Example, the substrate 40 thus prepared was subjected to Nielectroless plating. As an electroless plating solution, TOP NICORON RD,manufactured and sold by Okuno Chemical Industries Co., Ltd., was used.Thus, an Ni wiring composed of an Ni thin film having a thickness of 300nm was formed. The wiring had a fineness of 3 μm/3 μm in terms of aline/space.

Hereinabove, the present invention is described with reference to theembodiments and Examples, but the present invention is not limited tothese embodiments and Examples, and can be changed or modified.

For example, in the above embodiments and Examples, an example isdescribed in which the metal thin film 42 of a single layer is formed byelectroless plating, but the metal thin film may be composed of amultilayer film formed by performing the electroless plating two or moretimes. By virtue of having a multilayer structure, the metal thin filmmay be improved in corrosion resistance, electric properties,wettability, and the like, making it possible to form a metal thin filmhaving desired properties.

The metal thin film formed by embodiments of the present invention maybe applied to an electronic device using a metal electrode (e.g., thinfilm transistor or capacitor).

Further, with respect to the materials for and thicknesses of theindividual constituents and the deposition methods and depositionconditions and others described in the embodiments and Examples, thereis no particular limitation, and other materials and thicknesses andother deposition methods and deposition conditions can be used.

In the method for producing a metal thin film according to an embodimentof the present invention, the substrate to which the ink including acatalyst material has been transferred is subjected to electrolessplating, so that a metal thin film can be selectively formed on thesubstrate in a region to which the ink is transferred. The ink istransferred using a flat blanket, and further the substrate and the flatblanket are in contact by pressure compression in the transfer step.Consequently, the letterpress or substrate and the blanket are easy toalign and the whole pressure for the contact of them is uniform, therebyimproving the yield in producing a thin film. Further, the ink does notcontain a material for the metal thin film but a catalyst material forthe electroless plating. Accordingly, the metal thin film has a lowresistance and the pattern can be easily scaled down, as compared tothose obtained in a known method. Thus, a finer pattern and a higheryield than those obtained by a known method can be achieved withoutunnecessarily increasing the resistance of the thin film.

What is claimed is:
 1. A method for producing a thin film pattern on asubstrate, the method comprising: an application act of applying an inkto a flexible layer of a flat blanket, the flat blanket comprising theflexible layer and a rigid base; a first transfer act of bringing theflat blanket and a letterpress into contact by a pressure compressionwhile the flat blanket and the letterpress being disposed opposite eachother, to transfer a portion of the ink on the flat blanket to theletterpress, wherein the flat blanket is pushed toward the letterpressby compressed air from a back side of the flat blanket, wherein thecompressed air is supplied from a source provided by a stage that isfixed laterally relative to the letterpress, the flat blanket beingfixed to the stage at opposing locations with the source positionedbetween the opposing locations; a separation act after the firsttransfer act, wherein, the flat blanket and the letterpress areseparated by a vacuum evacuation of a space where the compressed air wassupplied; a second transfer act of bringing the flat blanket and thesubstrate into contact by pressure compression while the flat blanketand the substrate being disposed opposite each other, to transfer theink remaining on the flat blanket to the substrate.
 2. A methodaccording to claim 1, wherein the flat blanket and the substrate arebrought into contact by compressed air supplied on a back side of one ofthe flat blanket and the letterpress, in the second transfer act.
 3. Amethod according to claim 1, wherein a stretchable film is disposed atthe back side of the flat blanket, and in the first transfer act, thecompressed air is supplied at a back side of the stretchable film.
 4. Amethod according to claim 1, wherein: the flat blanket has a firstalignment mark; the substrate has a second alignment mark; and thesubstrate and the flat blanket are aligned by using the first alignmentmark and the second alignment mark in the second transfer act.
 5. Amethod according to claim 4, wherein at least a portion of a patternformed on the flat blanket in the first transfer act comprises the firstalignment mark.
 6. A method according to claim 1, further comprisingdepositing a metal thin film on the substrate.
 7. A method according toclaim 6, wherein depositing the metal thin film comprises selectivelydepositing the metal thin film over the transferred ink.
 8. A methodaccording to claim 7, wherein depositing the metal thin film comprisesimmersing the substrate in an electroless plating solution.
 9. A methodaccording to claim 8, further comprising annealing the metal thin filmin a vacuum or in an oxygen free atmosphere.
 10. A method according toclaim 1, wherein the second transfer act comprises the flat blanketbeing pushed toward the substrate by compressed air from a back side ofthe flat blanket, the compressed air supplied from the source that isfixed laterally relative to the substrate.
 11. A method according toclaim 1, wherein the ink includes a metal compound or metal fineparticles as a catalyst material for electroless plating, wherein themetal compound includes a metal bonded to an organic compound comprisingat least one of an alkylamine represented by a molecular formulaCH₃(CH₂)_(n)NH₂, a linear alkylthiol represented by a molecular formulaCH₃(CH₂)_(n)SH and an alkylnitrile, wherein n is an integer between 5and 40, and the metal fine particles include a surface covered with aprotective agent composed of the organic compound.